Sheng Xu

All Publications

• Wearable blood pressure sensors for cardiovascular monitoring and machine learning algorithms for blood pressure estimation. Nature reviews. Cardiology Min, S., An, J., Lee, J. H., Kim, J. H., Joe, D. J., Eom, S. H., Yoo, C. D., Ahn, H. S., Hwang, J. Y., Xu, S., Rogers, J. A., Lee, K. J. 2025; 22 (9): 629-648

  Abstract

  With advances in materials science and medical technology, wearable sensors have become crucial tools for the early diagnosis and continuous monitoring of numerous cardiovascular diseases, including arrhythmias, hypertension and coronary artery disease. These devices employ various sensing mechanisms, such as mechanoelectric, optoelectronic, ultrasonic and electrophysiological methods, to measure vital biosignals, including pulse rate, blood pressure and changes in heart rhythm. In this Review, we provide a comprehensive overview of the current state of wearable cardiovascular sensors, focusing particularly on those that measure blood pressure. We explore biosignal sensing principles, discuss blood pressure estimation methods (including machine learning algorithms) and summarize the latest advances in cuffless wearable blood pressure sensors. Finally, we highlight the challenges of and offer insights into potential pathways for the practical application of cuffless wearable blood pressure sensors in the medical field from both technical and clinical perspectives.

  View details for DOI 10.1038/s41569-025-01127-0

  View details for PubMedID 39966649

  View details for PubMedCentralID 5059018

• Wearable ultrasound technology NATURE REVIEWS BIOENGINEERING Zhou, S., Park, G., Lin, M., Yang, X., Xu, S. 2025; 3 (10): 835-854

  View details for DOI 10.1038/s44222-025-00329-y

  View details for Web of Science ID 001529116200001

• Integration of chemical and physical inputs for monitoring metabolites and cardiac signals in diabetes. Nature biomedical engineering Chang, A. Y., Lin, M., Yin, L., Reynoso, M., Ding, S., Liu, R., Dugas, Y., Casanova, A., Park, G., Li, Z., Luan, H., Askarinam, N., Zhang, F., Xu, S., Wang, J. 2025

  Abstract

  The development of closed-loop systems towards effective management of diabetes requires the inclusion of additional chemical and physical inputs that affect disease pathophysiology and reflect cardiovascular risks in patients. Comprehensive glycaemic control information should account for more than a single glucose signal. Here, we describe a hybrid flexible wristband sensing platform that integrates a microneedle array for multiplexed biomarker sensing and an ultrasonic array for blood pressure, arterial stiffness and heart-rate monitoring. The integrated system provides a continuous evaluation of the metabolic and cardiovascular status towards improving glycaemic control and alerting patients to cardiovascular risks. The multimodal platform offers continuous glucose, lactate and alcohol monitoring, along with simultaneous ultrasonic measurements of blood pressure, arterial stiffness and heart rate, to support understanding of the interplay between interstitial fluid biomarkers and physiological parameters during common activities. By expanding the continuous monitoring of patients with diabetes to additional biomarkers and key cardiac signals, our integrated multiplexed chemical-physical health-monitoring platform holds promise for addressing the limitations of existing single-modality glucose-monitoring systems towards enhanced management of diabetes and related cardiovascular risks.

  View details for DOI 10.1038/s41551-025-01439-z

  View details for PubMedID 40603746

  View details for PubMedCentralID 8126822

• A stealthy neural recorder for the study of behaviour in primates. Nature biomedical engineering Oh, S., Jekal, J., Won, J., Lim, K. S., Jeon, C. Y., Park, J., Yeo, H. G., Kim, Y. G., Lee, Y. H., Ha, L. J., Jung, H. H., Yea, J., Lee, H., Ha, J., Kim, J., Lee, D., Song, S., Son, J., Yu, T. S., Lee, J., Lee, S., Lee, J., Kim, B. H., Choi, J. W., Rah, J. C., Song, Y. M., Jeong, J. W., Choi, H. J., Xu, S., Lee, Y., Jang, K. I. 2025; 9 (6): 882-895

  Abstract

  By monitoring brain neural signals, neural recorders allow for the study of neurological mechanisms underlying specific behavioural and cognitive states. However, the large brain volumes of non-human primates and their extensive range of uncontrolled movements and inherent wildness make it difficult to carry out covert and long-term recording and analysis of deep-brain neural signals. Here we report the development and performance of a stealthy neural recorder for the study of naturalistic behaviours in non-human primates. The neural recorder includes a fully implantable wireless and battery-free module for the recording of local field potentials and accelerometry data in real time, a flexible 32-electrode neural probe with a resorbable insertion shuttle, and a repeater coil-based wireless-power-transfer system operating at the body scale. We used the device to record neurobehavioural data for over 1 month in a freely moving monkey and leveraged the recorded data to train an artificial intelligence model for the classification of the animals' eating behaviours.

  View details for DOI 10.1038/s41551-024-01280-w

  View details for PubMedID 39516303

  View details for PubMedCentralID PMC12176640

• Monitoring physical and mental activities with skin conductance: Wearables NATURE ELECTRONICS Wang, S., Guo, G., Xu, S. 2025; 8 (4): 294-295

  View details for DOI 10.1038/s41928-025-01373-7

  View details for Web of Science ID 001466355800001

• A wearable echomyography system based on a single transducer. Nature electronics Gao, X., Chen, X., Lin, M., Yue, W., Hu, H., Qin, S., Zhang, F., Lou, Z., Yin, L., Huang, H., Zhou, S., Bian, Y., Yang, X., Zhu, Y., Mu, J., Wang, X., Park, G., Lu, C., Wang, R., Wu, R. S., Wang, J., Li, J., Xu, S. 2024; 7 (11): 1035-1046

  Abstract

  Wearable electromyography devices can detect muscular activity for health monitoring and body motion tracking, but this approach is limited by weak and stochastic signals with a low spatial resolution. Alternatively, echomyography can detect muscle movement using ultrasound waves, but typically relies on complex transducer arrays, which are bulky, have high power consumption and can limit user mobility. Here we report a fully integrated wearable echomyography system that consists of a customized single transducer, a wireless circuit for data processing and an on-board battery for power. The system can be attached to the skin and provides accurate long-term wireless monitoring of muscles. To illustrate its capabilities, we use this system to detect the activity of the diaphragm, which allows the recognition of different breathing modes. We also develop a deep learning algorithm to correlate the single-transducer radio-frequency data from forearm muscles with hand gestures to accurately and continuously track 13 hand joints with a mean error of only 7.9°.

  View details for DOI 10.1038/s41928-024-01271-4

  View details for PubMedID 40677283

  View details for PubMedCentralID PMC12269893

• A fingertip-wearable microgrid system for autonomous energy management and metabolic monitoring NATURE ELECTRONICS Ding, S., Saha, T., Yin, L., Liu, R., Khan, M., Chang, A., Lee, H., Zhao, H., Liu, Y., Nazemi, A., Zhou, J., Chen, C., Li, Z., Zhang, C., Earney, S., Tang, S., Djassemi, O., Chen, X., Lin, M., Sandhu, S. S., Moon, J., Moonla, C., Nandhakumar, P., Park, Y., Mahato, K., Xu, S., Wang, J. 2024; 7 (9)

  View details for DOI 10.1038/s41928-024-01236-7

  View details for Web of Science ID 001303741500001

• Concepts and applications of digital twins in healthcare and medicine. Patterns (New York, N.Y.) Zhang, K., Zhou, H. Y., Baptista-Hon, D. T., Gao, Y., Liu, X., Oermann, E., Xu, S., Jin, S., Zhang, J., Sun, Z., Yin, Y., Razmi, R. M., Loupy, A., Beck, S., Qu, J., Wu, J. 2024; 5 (8): 101028

  Abstract

  The digital twin (DT) is a concept widely used in industry to create digital replicas of physical objects or systems. The dynamic, bi-directional link between the physical entity and its digital counterpart enables a real-time update of the digital entity. It can predict perturbations related to the physical object's function. The obvious applications of DTs in healthcare and medicine are extremely attractive prospects that have the potential to revolutionize patient diagnosis and treatment. However, challenges including technical obstacles, biological heterogeneity, and ethical considerations make it difficult to achieve the desired goal. Advances in multi-modal deep learning methods, embodied AI agents, and the metaverse may mitigate some difficulties. Here, we discuss the basic concepts underlying DTs, the requirements for implementing DTs in medicine, and their current and potential healthcare uses. We also provide our perspective on five hallmarks for a healthcare DT system to advance research in this field.

  View details for DOI 10.1016/j.patter.2024.101028

  View details for PubMedID 39233690

  View details for PubMedCentralID PMC11368703

• Wearable sensing of solid analytes. Nature materials Qin, S., Xu, S. 2024; 23 (8): 1019-1020

  View details for DOI 10.1038/s41563-024-01935-8

  View details for PubMedID 39090397

  View details for PubMedCentralID 9876798

• Clinical, Safety, and Engineering Perspectives on Wearable Ultrasound Technology: A Review. IEEE transactions on ultrasonics, ferroelectrics, and frequency control Song, P., Andre, M., Chitnis, P., Xu, S., Croy, T., Wear, K., Sikdar, S. 2024; 71 (7): 730-744

  Abstract

  Wearable ultrasound has the potential to become a disruptive technology enabling new applications not only in traditional clinical settings, but also in settings where ultrasound is not currently used. Understanding the basic engineering principles and limitations of wearable ultrasound is critical for clinicians, scientists, and engineers to advance potential applications and translate the technology from bench to bedside. Wearable ultrasound devices, especially monitoring devices, have the potential to apply acoustic energy to the body for far longer durations than conventional diagnostic ultrasound systems. Thus, bioeffects associated with prolonged acoustic exposure as well as skin health need to be carefully considered for wearable ultrasound devices. This article reviews emerging clinical applications, safety considerations, and future engineering and clinical research directions for wearable ultrasound technology.

  View details for DOI 10.1109/TUFFC.2023.3342150

  View details for PubMedID 38090856

  View details for PubMedCentralID PMC11416895

• Emerging Wearable Ultrasound Technology. IEEE transactions on ultrasonics, ferroelectrics, and frequency control Huang, H., Wu, R. S., Lin, M., Xu, S. 2024; 71 (7): 713-729

  Abstract

  This perspective article provides a brief overview on materials, fabrications, beamforming, and applications for wearable ultrasound devices, a rapidly growing field with versatile implications. Recent developments in miniaturization and soft electronics have significantly advanced wearable ultrasound devices. Such devices offer distinctive advantages over traditional ultrasound probes, including prolonged usability and operator independence, and have demonstrated their effectiveness in continuous monitoring, noninvasive therapies, and advanced human-machine interfaces. Wearable ultrasound devices can be classified into three main categories: rigid, flexible, and stretchable, each having distinctive properties and fabrication strategies. Key unique strategies in device design, packaging, and beamforming for each type of wearable ultrasound devices are reviewed. Furthermore, we highlight the latest applications enabled by wearable ultrasound technology in various areas. This article concludes by discussing the outstanding challenges within the field and outlines potential pathways for future advancements.

  View details for DOI 10.1109/TUFFC.2023.3327143

  View details for PubMedID 37878424

  View details for PubMedCentralID PMC11263711

• Transcranial volumetric imaging using a conformal ultrasound patch. Nature Zhou, S., Gao, X., Park, G., Yang, X., Qi, B., Lin, M., Huang, H., Bian, Y., Hu, H., Chen, X., Wu, R. S., Liu, B., Yue, W., Lu, C., Wang, R., Bheemreddy, P., Qin, S., Lam, A., Wear, K. A., Andre, M., Kistler, E. B., Newell, D. W., Xu, S. 2024; 629 (8013): 810-818

  Abstract

  Accurate and continuous monitoring of cerebral blood flow is valuable for clinical neurocritical care and fundamental neurovascular research. Transcranial Doppler (TCD) ultrasonography is a widely used non-invasive method for evaluating cerebral blood flow1, but the conventional rigid design severely limits the measurement accuracy of the complex three-dimensional (3D) vascular networks and the practicality for prolonged recording2. Here we report a conformal ultrasound patch for hands-free volumetric imaging and continuous monitoring of cerebral blood flow. The 2 MHz ultrasound waves reduce the attenuation and phase aberration caused by the skull, and the copper mesh shielding layer provides conformal contact to the skin while improving the signal-to-noise ratio by 5 dB. Ultrafast ultrasound imaging based on diverging waves can accurately render the circle of Willis in 3D and minimize human errors during examinations. Focused ultrasound waves allow the recording of blood flow spectra at selected locations continuously. The high accuracy of the conformal ultrasound patch was confirmed in comparison with a conventional TCD probe on 36 participants, showing a mean difference and standard deviation of difference as -1.51 ± 4.34 cm s-1, -0.84 ± 3.06 cm s-1 and -0.50 ± 2.55 cm s-1 for peak systolic velocity, mean flow velocity, and end diastolic velocity, respectively. The measurement success rate was 70.6%, compared with 75.3% for a conventional TCD probe. Furthermore, we demonstrate continuous blood flow spectra during different interventions and identify cascades of intracranial B waves during drowsiness within 4 h of recording.

  View details for DOI 10.1038/s41586-024-07381-5

  View details for PubMedID 38778234

  View details for PubMedCentralID PMC11875229

• In-ear integrated sensor array for the continuous monitoring of brain activity and of lactate in sweat. Nature biomedical engineering Xu, Y., De la Paz, E., Paul, A., Mahato, K., Sempionatto, J. R., Tostado, N., Lee, M., Hota, G., Lin, M., Uppal, A., Chen, W., Dua, S., Yin, L., Wuerstle, B. L., Deiss, S., Mercier, P., Xu, S., Wang, J., Cauwenberghs, G. 2023; 7 (10): 1307-1320

  Abstract

  Owing to the proximity of the ear canal to the central nervous system, in-ear electrophysiological systems can be used to unobtrusively monitor brain states. Here, by taking advantage of the ear's exocrine sweat glands, we describe an in-ear integrated array of electrochemical and electrophysiological sensors placed on a flexible substrate surrounding a user-generic earphone for the simultaneous monitoring of lactate concentration and brain states via electroencephalography, electrooculography and electrodermal activity. In volunteers performing an acute bout of exercise, the device detected elevated lactate levels in sweat concurrently with the modulation of brain activity across all electroencephalography frequency bands. Simultaneous and continuous unobtrusive in-ear monitoring of metabolic biomarkers and brain electrophysiology may allow for the discovery of dynamic and synergetic interactions between brain and body biomarkers in real-world settings for long-term health monitoring or for the detection or monitoring of neurodegenerative diseases.

  View details for DOI 10.1038/s41551-023-01095-1

  View details for PubMedID 37770754

  View details for PubMedCentralID PMC10589098

• Stretchable ultrasonic arrays for the three-dimensional mapping of the modulus of deep tissue. Nature biomedical engineering Hu, H., Ma, Y., Gao, X., Song, D., Li, M., Huang, H., Qian, X., Wu, R., Shi, K., Ding, H., Lin, M., Chen, X., Zhao, W., Qi, B., Zhou, S., Chen, R., Gu, Y., Chen, Y., Lei, Y., Wang, C., Wang, C., Tong, Y., Cui, H., Abdal, A., Zhu, Y., Tian, X., Chen, Z., Lu, C., Yang, X., Mu, J., Lou, Z., Eghtedari, M., Zhou, Q., Oberai, A., Xu, S. 2023; 7 (10): 1321-1334

  Abstract

  Serial assessment of the biomechanical properties of tissues can be used to aid the early detection and management of pathophysiological conditions, to track the evolution of lesions and to evaluate the progress of rehabilitation. However, current methods are invasive, can be used only for short-term measurements, or have insufficient penetration depth or spatial resolution. Here we describe a stretchable ultrasonic array for performing serial non-invasive elastographic measurements of tissues up to 4 cm beneath the skin at a spatial resolution of 0.5 mm. The array conforms to human skin and acoustically couples with it, allowing for accurate elastographic imaging, which we validated via magnetic resonance elastography. We used the device to map three-dimensional distributions of the Young's modulus of tissues ex vivo, to detect microstructural damage in the muscles of volunteers before the onset of soreness and to monitor the dynamic recovery process of muscle injuries during physiotherapies. The technology may facilitate the diagnosis and treatment of diseases affecting tissue biomechanics.

  View details for DOI 10.1038/s41551-023-01038-w

  View details for PubMedID 37127710

  View details for PubMedCentralID 6636265

• Strategic heating for growing perovskite single crystals MATTER Lu, C., Wang, R., Xu, S. 2023; 6 (8): 2537-2539

  View details for DOI 10.1016/j.matt.2023.05.039

  View details for Web of Science ID 001052743500001

• A fully integrated wearable ultrasound system to monitor deep tissues in moving subjects. Nature biotechnology Lin, M., Zhang, Z., Gao, X., Bian, Y., Wu, R. S., Park, G., Lou, Z., Zhang, Z., Xu, X., Chen, X., Kang, A., Yang, X., Yue, W., Yin, L., Wang, C., Qi, B., Zhou, S., Hu, H., Huang, H., Li, M., Gu, Y., Mu, J., Yang, A., Yaghi, A., Chen, Y., Lei, Y., Lu, C., Wang, R., Wang, J., Xiang, S., Kistler, E. B., Vasconcelos, N., Xu, S. 2023

  Abstract

  Recent advances in wearable ultrasound technologies have demonstrated the potential for hands-free data acquisition, but technical barriers remain as these probes require wire connections, can lose track of moving targets and create data-interpretation challenges. Here we report a fully integrated autonomous wearable ultrasonic-system-on-patch (USoP). A miniaturized flexible control circuit is designed to interface with an ultrasound transducer array for signal pre-conditioning and wireless data communication. Machine learning is used to track moving tissue targets and assist the data interpretation. We demonstrate that the USoP allows continuous tracking of physiological signals from tissues as deep as 164mm. On mobile subjects, the USoP can continuously monitor physiological signals, including central blood pressure, heart rate and cardiac output, for as long as 12h. This result enables continuous autonomous surveillance of deep tissue signals toward the internet-of-medical-things.

  View details for DOI 10.1038/s41587-023-01800-0

  View details for PubMedID 37217752

• Technology Roadmap for Flexible Sensors. ACS nano Luo, Y., Abidian, M. R., Ahn, J. H., Akinwande, D., Andrews, A. M., Antonietti, M., Bao, Z., Berggren, M., Berkey, C. A., Bettinger, C. J., Chen, J., Chen, P., Cheng, W., Cheng, X., Choi, S. J., Chortos, A., Dagdeviren, C., Dauskardt, R. H., Di, C. A., Dickey, M. D., Duan, X., Facchetti, A., Fan, Z., Fang, Y., Feng, J., Feng, X., Gao, H., Gao, W., Gong, X., Guo, C. F., Guo, X., Hartel, M. C., He, Z., Ho, J. S., Hu, Y., Huang, Q., Huang, Y., Huo, F., Hussain, M. M., Javey, A., Jeong, U., Jiang, C., Jiang, X., Kang, J., Karnaushenko, D., Khademhosseini, A., Kim, D. H., Kim, I. D., Kireev, D., Kong, L., Lee, C., Lee, N. E., Lee, P. S., Lee, T. W., Li, F., Li, J., Liang, C., Lim, C. T., Lin, Y., Lipomi, D. J., Liu, J., Liu, K., Liu, N., Liu, R., Liu, Y., Liu, Y., Liu, Z., Liu, Z., Loh, X. J., Lu, N., Lv, Z., Magdassi, S., Malliaras, G. G., Matsuhisa, N., Nathan, A., Niu, S., Pan, J., Pang, C., Pei, Q., Peng, H., Qi, D., Ren, H., Rogers, J. A., Rowe, A., Schmidt, O. G., Sekitani, T., Seo, D. G., Shen, G., Sheng, X., Shi, Q., Someya, T., Song, Y., Stavrinidou, E., Su, M., Sun, X., Takei, K., Tao, X. M., Tee, B. C., Thean, A. V., Trung, T. Q., Wan, C., Wang, H., Wang, J., Wang, M., Wang, S., Wang, T., Wang, Z. L., Weiss, P. S., Wen, H., Xu, S., Xu, T., Yan, H., Yan, X., Yang, H., Yang, L., Yang, S., Yin, L., Yu, C., Yu, G., Yu, J., Yu, S. H., Yu, X., Zamburg, E., Zhang, H., Zhang, X., Zhang, X., Zhang, X., Zhang, Y., Zhang, Y., Zhao, S., Zhao, X., Zheng, Y., Zheng, Y. Q., Zheng, Z., Zhou, T., Zhu, B., Zhu, M., Zhu, R., Zhu, Y., Zhu, Y., Zou, G., Chen, X. 2023

  Abstract

  Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.

  View details for DOI 10.1021/acsnano.2c12606

  View details for PubMedID 36892156

• A wearable cardiac ultrasound imager. Nature Hu, H., Huang, H., Li, M., Gao, X., Yin, L., Qi, R., Wu, R. S., Chen, X., Ma, Y., Shi, K., Li, C., Maus, T. M., Huang, B., Lu, C., Lin, M., Zhou, S., Lou, Z., Gu, Y., Chen, Y., Lei, Y., Wang, X., Wang, R., Yue, W., Yang, X., Bian, Y., Mu, J., Park, G., Xiang, S., Cai, S., Corey, P. W., Wang, J., Xu, S. 2023; 613 (7945): 667-675

  Abstract

  Continuous imaging of cardiac functions is highly desirable for the assessment of long-term cardiovascular health, detection of acute cardiac dysfunction and clinical management of critically ill or surgical patients1-4. However, conventional non-invasive approaches to image the cardiac function cannot provide continuous measurements owing to device bulkiness5-11, and existing wearable cardiac devices can only capture signals on the skin12-16. Here we report a wearable ultrasonic device for continuous, real-time and direct cardiac function assessment. We introduce innovations in device design and material fabrication that improve the mechanical coupling between the device and human skin, allowing the left ventricle to be examined from different views during motion. We also develop a deep learning model that automatically extracts the left ventricular volume from the continuous image recording, yielding waveforms of key cardiac performance indices such as stroke volume, cardiac output and ejection fraction. This technology enables dynamic wearable monitoring of cardiac performance with substantially improved accuracy in various environments.

  View details for DOI 10.1038/s41586-022-05498-z

  View details for PubMedID 36697864

• A photoacoustic patch for three-dimensional imaging of hemoglobin and core temperature. Nature communications Gao, X., Chen, X., Hu, H., Wang, X., Yue, W., Mu, J., Lou, Z., Zhang, R., Shi, K., Chen, X., Lin, M., Qi, B., Zhou, S., Lu, C., Gu, Y., Yang, X., Ding, H., Zhu, Y., Huang, H., Ma, Y., Li, M., Mishra, A., Wang, J., Xu, S. 2022; 13 (1): 7757

  Abstract

  Electronic patches, based on various mechanisms, allow continuous and noninvasive monitoring of biomolecules on the skin surface. However, to date, such devices are unable to sense biomolecules in deep tissues, which have a stronger and faster correlation with the human physiological status than those on the skin surface. Here, we demonstrate a photoacoustic patch for three-dimensional (3D) mapping of hemoglobin in deep tissues. This photoacoustic patch integrates an array of ultrasonic transducers and vertical-cavity surface-emitting laser (VCSEL) diodes on a common soft substrate. The high-power VCSEL diodes can generate laser pulses that penetrate >2 cm into biological tissues and activate hemoglobin molecules to generate acoustic waves, which can be collected by the transducers for 3D imaging of the hemoglobin with a high spatial resolution. Additionally, the photoacoustic signal amplitude and temperature have a linear relationship, which allows 3D mapping of core temperatures with high accuracy and fast response. With access to biomolecules in deep tissues, this technology adds unprecedented capabilities to wearable electronics and thus holds significant implications for various applications in both basic research and clinical practice.

  View details for DOI 10.1038/s41467-022-35455-3

  View details for PubMedID 36522334

  View details for PubMedCentralID PMC9755152

• A stretchable epidermal sweat sensing platform with an integrated printed battery and electrochromic display NATURE ELECTRONICS Yin, L., Cao, M., Kim, K., Lin, M., Moon, J., Sempionatto, J. R., Yu, J., Liu, R., Wicker, C., Trifonov, A., Zhang, F., Hu, H., Moreto, J. R., Go, J., Xu, S., Wang, J. 2022; 5 (10): 694-705

  View details for DOI 10.1038/s41928-022-00843-6

  View details for Web of Science ID 000864545200001

• Perovskite superlattices with efficient carrier dynamics. Nature Lei, Y., Li, Y., Lu, C., Yan, Q., Wu, Y., Babbe, F., Gong, H., Zhang, S., Zhou, J., Wang, R., Zhang, R., Chen, Y., Tsai, H., Gu, Y., Hu, H., Lo, Y., Nie, W., Lee, T., Luo, J., Yang, K., Jang, K., Xu, S. 2022; 608 (7922): 317-323

  Abstract

  Compared with their three-dimensional (3D) counterparts, low-dimensional metal halide perovskites (2D and quasi-2D; B2An-1MnX3n+1, such as B=R-NH3+, A=HC(NH2)2+, Cs+; M=Pb2+, Sn2+; X=Cl-, Br-, I-) with periodic inorganic-organic structures have shown promising stability and hysteresis-free electrical performance1-6. However, their unique multiple-quantum-well structure limits the device efficiencies because of the grain boundaries and randomlyoriented quantum wells in polycrystals7. In single crystals, the carrier transport through the thickness direction is hindered by the layered insulating organic spacers8. Furthermore, the strong quantum confinement from the organic spacers limits the generation and transport of free carriers9,10. Also, lead-free metal halide perovskites have been developed but their device performance is limited by their low crystallinity and structural instability11. Here we report a low-dimensional metal halide perovskite BA2MAn-1SnnI3n+1 (BA, butylammonium; MA, methylammonium; n=1,3,5) superlattice by chemical epitaxy. The inorganic slabs are aligned vertical to the substrate and interconnected in a criss-cross 2D network parallel to the substrate, leading to efficient carrier transport in three dimensions. A lattice-mismatched substrate compresses the organic spacers, which weakens the quantum confinement. The performance of a superlattice solar cell has been certified under the quasi-steady state, showing a stable 12.36% photoelectric conversion efficiency. Moreover, an intraband exciton relaxation process may have yielded an unusually high open-circuit voltage (VOC).

  View details for DOI 10.1038/s41586-022-04961-1

  View details for PubMedID 35948711

• Soft wearable devices for deep-tissue sensing NATURE REVIEWS MATERIALS Lin, M., Hu, H., Zhou, S., Xu, S. 2022; 7 (11): 850-869

  View details for DOI 10.1038/s41578-022-00427-y

  View details for Web of Science ID 000768653600001

• Three-dimensional transistor arrays for intra- and inter-cellular recording NATURE NANOTECHNOLOGY Gu, Y., Wang, C., Kim, N., Zhang, J., Wang, T., Stowe, J., Nasiri, R., Li, J., Zhang, D., Yang, A., Hsu, L., Dai, X., Mu, J., Liu, Z., Lin, M., Li, W., Wang, C., Gong, H., Chen, Y., Lei, Y., Hu, H., Li, Y., Zhang, L., Huang, Z., Zhang, X., Ahadian, S., Banik, P., Zhang, L., Jiang, X., Burke, P. J., Khademhosseini, A., McCulloch, A. D., Xu, S. 2022; 17 (3): 292-+

  Abstract

  Electrical impulse generation and its conduction within cells or cellular networks are the cornerstone of electrophysiology. However, the advancement of the field is limited by sensing accuracy and the scalability of current recording technologies. Here we describe a scalable platform that enables accurate recording of transmembrane potentials in electrogenic cells. The platform employs a three-dimensional high-performance field-effect transistor array for minimally invasive cellular interfacing that produces faithful recordings, as validated by the gold standard patch clamp. Leveraging the high spatial and temporal resolutions of the field-effect transistors, we measured the intracellular signal conduction velocity of a cardiomyocyte to be 0.182 m s-1, which is about five times the intercellular velocity. We also demonstrate intracellular recordings in cardiac muscle tissue constructs and reveal the signal conduction paths. This platform could provide new capabilities in probing the electrical behaviours of single cells and cellular networks, which carries broad implications for understanding cellular physiology, pathology and cell-cell interactions.

  View details for DOI 10.1038/s41565-021-01040-w

  View details for Web of Science ID 000734148200004

  View details for PubMedID 34949774

  View details for PubMedCentralID PMC8994210

• Demystifying phase transformations in metal halide perovskites MATTER Lu, C., Wang, Y., Zhang, R., Xu, S. 2021; 4 (8): 2627-2629

  View details for DOI 10.1016/j.matt.2021.06.026

  View details for Web of Science ID 000684230000023

• A passive perspiration biofuel cell: High energy return on investment JOULE Yin, L., Moon, J., Sempionatto, J. R., Lin, M., Cao, M., Trifonov, A., Zhang, F., Lou, Z., Jeong, J., Lee, S., Xu, S., Wang, J. 2021; 5 (7): 1888-1904

  View details for DOI 10.1016/j.joule.2021.06.004

  View details for Web of Science ID 000675889700019

• Review Single-crystal halide perovskites: Opportunities and challenges MATTER Lei, Y., Chen, Y., Xu, S. 2021; 4 (7): 2266-2308

  View details for DOI 10.1016/j.matt.2021.05.002

  View details for Web of Science ID 000670754800001

• Wearable Biosupercapacitor: Harvesting and Storing Energy from Sweat ADVANCED FUNCTIONAL MATERIALS Lv, J., Yin, L., Chen, X., Jeerapan, I., Silva, C. A., Li, Y., Le, M., Lin, Z., Wang, L., Trifonov, A., Xu, S., Cosnier, S., Wang, J. 2021; 31 (38)

  View details for DOI 10.1002/adfm.202102915

  View details for Web of Science ID 000669390100001

• Continuous monitoring of deep-tissue haemodynamics with stretchable ultrasonic phased arrays NATURE BIOMEDICAL ENGINEERING Wang, C., Qi, B., Lin, M., Zhang, Z., Makihata, M., Liu, B., Zhou, S., Huang, Y., Hu, H., Gu, Y., Chen, Y., Lei, Y., Lee, T., Chien, S., Jang, K., Kistler, E. B., Xu, S. 2021; 5 (7): 749-+

  View details for DOI 10.1038/s41551-021-00763-4

  View details for Web of Science ID 000673384000013

• An epidermal patch for the simultaneous monitoring of haemodynamic and metabolic biomarkers. Nature biomedical engineering Sempionatto, J. R., Lin, M., Yin, L., De la Paz, E., Pei, K., Sonsa-Ard, T., de Loyola Silva, A. N., Khorshed, A. A., Zhang, F., Tostado, N., Xu, S., Wang, J. 2021; 5 (7): 737-748

  Abstract

  Monitoring the effects of daily activities on the physiological responses of the body calls for wearable devices that can simultaneously track metabolic and haemodynamic parameters. Here we describe a non-invasive skin-worn device for the simultaneous monitoring of blood pressure and heart rate via ultrasonic transducers and of multiple biomarkers via electrochemical sensors. We optimized the integrated device so that it provides mechanical resiliency and flexibility while conforming to curved skin surfaces, and to ensure reliable sensing of glucose in interstitial fluid and of lactate, caffeine and alcohol in sweat, without crosstalk between the individual sensors. In human volunteers, the device captured physiological effects of food intake and exercise, in particular the production of glucose after food digestion, the consumption of glucose via glycolysis, and increases in blood pressure and heart rate compensating for oxygen depletion and lactate generation. Continuous and simultaneous acoustic and electrochemical sensing via integrated wearable devices should enrich the understanding of the body's response to daily activities, and could facilitate the early prediction of abnormal physiological changes.

  View details for DOI 10.1038/s41551-021-00685-1

  View details for PubMedID 33589782

  View details for PubMedCentralID 8183422

• Instant, multiscale dry transfer printing by atomic diffusion control at heterogeneous interfaces. Science advances Heo, S., Ha, J., Son, S. J., Choi, I. S., Lee, H., Oh, S., Jekal, J., Kang, M. H., Lee, G. J., Jung, H. H., Yea, J., Lee, T., Lee, Y., Choi, J. W., Xu, S., Choi, J. H., Jeong, J. W., Song, Y. M., Rah, J. C., Keum, H., Jang, K. I. 2021; 7 (28)

  Abstract

  Transfer printing is a technique that integrates heterogeneous materials by readily retrieving functional elements from a grown substrate and subsequently printing them onto a specific target site. These strategies are broadly exploited to construct heterogeneously integrated electronic devices. A typical wet transfer printing method exhibits limitations related to unwanted displacement and shape distortion of the device due to uncontrollable fluid movement and slow chemical diffusion. In this study, a dry transfer printing technique that allows reliable and instant release of devices by exploiting the thermal expansion mismatch between adjacent materials is demonstrated, and computational studies are conducted to investigate the fundamental mechanisms of the dry transfer printing process. Extensive exemplary demonstrations of multiscale, sequential wet-dry, circuit-level, and biological topography-based transfer printing demonstrate the potential of this technique for many other emerging applications in modern electronics that have not been achieved through conventional wet transfer printing over the past few decades.

  View details for DOI 10.1126/sciadv.abh0040

  View details for PubMedID 34244149

  View details for PubMedCentralID PMC8270493

• Smart Contact Lenses for Biosensing Applications ADVANCED INTELLIGENT SYSTEMS Ma, X., Ahadian, S., Liu, S., Zhang, J., Liu, S., Cao, T., Lin, W., Wu, D., de Barros, N., Zare, M., Diltemiz, S., Jucaud, V., Zhu, Y., Zhang, S., Banton, E., Gu, Y., Nan, K., Xu, S., Dokmeci, M., Khademhosseini, A. 2021; 3 (5)

  View details for DOI 10.1002/aisy.202000263

  View details for Web of Science ID 000669810200010

• Fabric-substrated capacitive biopotential sensors enhanced by dielectric nanoparticles NANO RESEARCH Chen, X., Gao, X., Nomoto, A., Shi, K., Lin, M., Hu, H., Gu, Y., Zhu, Y., Wu, Z., Chen, X., Wang, X., Qi, B., Zhou, S., Ding, H., Xu, S. 2021; 14 (9): 3248-3252

  View details for DOI 10.1007/s12274-021-3458-0

  View details for Web of Science ID 000640147500003

• Nanomaterial Biointerfacing via Mitochondrial Membrane Coating for Targeted Detoxification and Molecular Detection. Nano letters Gong, H., Zhang, Q., Komarla, A., Wang, S., Duan, Y., Zhou, Z., Chen, F., Fang, R. H., Xu, S., Gao, W., Zhang, L. 2021; 21 (6): 2603-2609

  Abstract

  Natural cell membranes derived from various cell sources have been successfully utilized to coat nanomaterials for functionalization. However, intracellular membranes from the organelles of eukaryotes remain unexplored. Herein, we choose mitochondrion as a representative cell organelle and coat outer mitochondrial membrane (OMM) from mouse livers onto nanoparticles and field-effect transistors (FETs) through a membrane vesicle-substrate fusion process. Polymeric nanoparticles coated with OMM (OMM-NPs) can bind with ABT-263, a B-cell lymphoma protein 2 (Bcl-2) inhibitor that targets the OMM. As a result, OMM-NPs effectively protect the cells from ABT-263 induced cell death and apoptosis in vitro and attenuated ABT-263-induced thrombocytopenia in vivo. Meanwhile, FET sensors coated with OMM (OMM-FETs) can detect and distinguish anti-Bcl-2 antibody and small molecule agonists. Overall, these results show that OMM can be coated onto the surfaces of both nanoparticles and functional devices, suggesting that intracellular membranes can be used as coating materials for novel biointerfacing.

  View details for DOI 10.1021/acs.nanolett.1c00238

  View details for PubMedID 33687220

• A self-sustainable wearable multi-modular E-textile bioenergy microgrid system. Nature communications Yin, L., Kim, K. N., Lv, J., Tehrani, F., Lin, M., Lin, Z., Moon, J. M., Ma, J., Yu, J., Xu, S., Wang, J. 2021; 12 (1): 1542

  Abstract

  Despite the fast development of various energy harvesting and storage devices, their judicious integration into efficient, autonomous, and sustainable wearable systems has not been widely explored. Here, we introduce the concept and design principles of e-textile microgrids by demonstrating a multi-module bioenergy microgrid system. Unlike earlier hybrid wearable systems, the presented e-textile microgrid relies solely on human activity to work synergistically, harvesting biochemical and biomechanical energy using sweat-based biofuel cells and triboelectric generators, and regulating the harvested energy via supercapacitors for high-power output. Through energy budgeting, the e-textile system can efficiently power liquid crystal displays continuously or a sweat sensor-electrochromic display system in pulsed sessions, with half the booting time and triple the runtime in a 10-min exercise session. Implementing "compatible form factors, commensurate performance, and complementary functionality" design principles, the flexible, textile-based bioenergy microgrid offers attractive prospects for the design and operation of efficient, sustainable, and autonomous wearable systems.

  View details for DOI 10.1038/s41467-021-21701-7

  View details for PubMedID 33750816

  View details for PubMedCentralID PMC7943583

• Role of the Metal-Semiconductor Interface in Halide Perovskite Devices for Radiation Photon Counting. ACS applied materials & interfaces Shrestha, S., Tsai, H., Yoho, M., Ghosh, D., Liu, F., Lei, Y., Tisdale, J., Baldwin, J., Xu, S., Neukirch, A. J., Tretiak, S., Vo, D., Nie, W. 2020; 12 (40): 45533-45540

  Abstract

  Halide perovskites are promising optoelectronic semiconductors. For applications in solid-state detectors that operate in low photon flux counting mode, blocking interfaces are essential to minimize the dark current noise. Here, we investigate the interface between methylammonium lead tri-iodide (MAPbI3) single crystals and commonly used high and low work function metals to achieve photon counting capabilities in a solid-state detector. Using scanning photocurrent microscopy, we observe a large Schottky barrier at the MAPbI3/Pb interface, which efficiently blocks dark current. Moreover, the shape of the photocurrent profile indicates that the MAPbI3 single-crystal surface has a deep fermi level close to that of Au. Rationalized by first-principle calculations, we attribute this observation to the defects due to excess iodine on the surface underpinning emergence of deep band-edge states. The photocurrent decay profile yields a charge carrier diffusion length of 10-25 μm. Using this knowledge, we demonstrate a single-crystal MAPbI3 detector that can count single γ-ray photons by producing sharp electrical pulses with a fast rise time of <2 μs. Our study indicates that the interface plays a crucial role in solid-state detectors operating in photon counting mode.

  View details for DOI 10.1021/acsami.0c11805

  View details for PubMedID 32886475

• Deciphering facial movements. Nature biomedical engineering Gao, X., Chen, X., Xu, S. 2020; 4 (10): 935-936

  View details for DOI 10.1038/s41551-020-00629-1

  View details for PubMedID 33093666

• A fabrication process for flexible single-crystal perovskite devices. Nature Lei, Y., Chen, Y., Zhang, R., Li, Y., Yan, Q., Lee, S., Yu, Y., Tsai, H., Choi, W., Wang, K., Luo, Y., Gu, Y., Zheng, X., Wang, C., Wang, C., Hu, H., Li, Y., Qi, B., Lin, M., Zhang, Z., Dayeh, S. A., Pharr, M., Fenning, D. P., Lo, Y. H., Luo, J., Yang, K., Yoo, J., Nie, W., Xu, S. 2020; 583 (7818): 790-795

  Abstract

  Organic-inorganic hybrid perovskites have electronic and optoelectronic properties that make them appealing in many device applications1-4. Although many approaches focus on polycrystalline materials5-7, single-crystal hybrid perovskites show improved carrier transport and enhanced stability over their polycrystalline counterparts, due to their orientation-dependent transport behaviour8-10 and lower defect concentrations11,12. However, the fabrication of single-crystal hybrid perovskites, and controlling their morphology and composition, are challenging12. Here we report a solution-based lithography-assisted epitaxial-growth-and-transfer method for fabricating single-crystal hybrid perovskites on arbitrary substrates, with precise control of their thickness (from about 600 nanometres to about 100 micrometres), area (continuous thin films up to about 5.5 centimetres by 5.5 centimetres), and composition gradient in the thickness direction (for example, from methylammonium lead iodide, MAPbI3, to MAPb0.5Sn0.5I3). The transferred single-crystal hybrid perovskites are of comparable quality to those directly grown on epitaxial substrates, and are mechanically flexible depending on the thickness. Lead-tin gradient alloying allows the formation of a graded electronic bandgap, which increases the carrier mobility and impedes carrier recombination. Devices based on these single-crystal hybrid perovskites show not only high stability against various degradation factors but also good performance (for example, solar cells based on lead-tin-gradient structures with an average efficiency of 18.77 per cent).

  View details for DOI 10.1038/s41586-020-2526-z

  View details for PubMedID 32728239

• Stretchable Nanolayered Thermoelectric Energy Harvester on Complex and Dynamic Surfaces. Nano letters Yang, Y., Hu, H., Chen, Z., Wang, Z., Jiang, L., Lu, G., Li, X., Chen, R., Jin, J., Kang, H., Chen, H., Lin, S., Xiao, S., Zhao, H., Xiong, R., Shi, J., Zhou, Q., Xu, S., Chen, Y. 2020; 20 (6): 4445-4453

  Abstract

  Thermoelectric generators (TEGs) provide a unique solution for energy harvesting from waste heat, presenting a potential solution for green energy. However, traditional rigid and flexible TEGs cannot work on complex and dynamic surfaces. Here, we report a stretchable TEG (S-TEG) (over 50% stretchability of the entire device) that is geometrically suitable for various complex and dynamic surfaces of heat sources. The S-TEG consists of hot-pressed nanolayered p-(Sb2Te3) and n-(Bi2Te3)-type thermoelectric couple arrays and exploits the wavy serpentine interconnects to integrate all units. The internal resistance of a 10 × 10 array is 22 ohm, and the output power is ∼0.15 mW/cm2 at ΔT = 19 K on both developable and nondevelopable surfaces, which are much improved compared with those of existing S-TEGs. The energy harvesting of S-TEG from the dynamic surfaces of the human skin offers a potential energy solution for the wearable devices for health monitoring.

  View details for DOI 10.1021/acs.nanolett.0c01225

  View details for PubMedID 32368921

• Frequency- and Power-Dependent Photoresponse of a Perovskite Photodetector Down to the Single-Photon Level. Nano letters Xu, Z., Yu, Y., Arya, S., Niaz, I. A., Chen, Y., Lei, Y., Miah, M. A., Zhou, J., Zhang, A. C., Yan, L., Xu, S., Nomura, K., Lo, Y. H. 2020; 20 (3): 2144-2151

  Abstract

  Organometallic halide perovskites attract strong interests for their high photoresponsivity and solar cell efficiency. However, there was no systematic study of their power- and frequency-dependent photoresponsivity. We identified two different power-dependent photoresponse types in methylammonium lead iodide perovskite (MAPbI3) photodetectors. In the first type, the photoresponse remains constant from 5 Hz to 800 MHz. In the second type, absorption of a single photon can generate a persistent photoconductivity of 30 pA under an applied electric field of 2.5 × 104 V/cm. Additional absorbed photons, up to 8, linearly increase the persistent photoconductivity, which saturates with the absorption of more than 10 photons. This is different than single-photon avalanche detectors (SPADs) because the single-photon response is persistent as long as the device is under bias, providing unique opportunities for novel electronic and photonic devices such as analogue memories for neuromorphic computing. We propose an avalanche-like process for iodine ions and estimate that absorption of a single 0.38 aJ photon triggers the motion of 108-9 ions, resulting in accumulations of ions and charged vacancies at the MAPbI3/electrode interfaces to cause the band bending and change of electric material properties. We have made the first observation that single-digit photon absorption can alter the macroscopic electric and optoelectronic properties of a perovskite thin film.

  View details for DOI 10.1021/acs.nanolett.0c00161

  View details for PubMedID 32026675

• Strain engineering and epitaxial stabilization of halide perovskites. Nature Chen, Y., Lei, Y., Li, Y., Yu, Y., Cai, J., Chiu, M. H., Rao, R., Gu, Y., Wang, C., Choi, W., Hu, H., Wang, C., Li, Y., Song, J., Zhang, J., Qi, B., Lin, M., Zhang, Z., Islam, A. E., Maruyama, B., Dayeh, S., Li, L. J., Yang, K., Lo, Y. H., Xu, S. 2020; 577 (7789): 209-215

  Abstract

  Strain engineering is a powerful tool with which to enhance semiconductor device performance1,2. Halide perovskites have shown great promise in device applications owing to their remarkable electronic and optoelectronic properties3-5. Although applying strain to halide perovskites has been frequently attempted, including using hydrostatic pressurization6-8, electrostriction9, annealing10-12, van der Waals force13, thermal expansion mismatch14, and heat-induced substrate phase transition15, the controllable and device-compatible strain engineering of halide perovskites by chemical epitaxy remains a challenge, owing to the absence of suitable lattice-mismatched epitaxial substrates. Here we report the strained epitaxial growth of halide perovskite single-crystal thin films on lattice-mismatched halide perovskite substrates. We investigated strain engineering of α-formamidinium lead iodide (α-FAPbI3) using both experimental techniques and theoretical calculations. By tailoring the substrate composition-and therefore its lattice parameter-a compressive strain as high as 2.4 per cent is applied to the epitaxial α-FAPbI3 thin film. We demonstrate that this strain effectively changes the crystal structure, reduces the bandgap and increases the hole mobility of α-FAPbI3. Strained epitaxy is also shown to have a substantial stabilization effect on the α-FAPbI3 phase owing to the synergistic effects of epitaxial stabilization and strain neutralization. As an example, strain engineering is applied to enhance the performance of an α-FAPbI3-based photodetector.

  View details for DOI 10.1038/s41586-019-1868-x

  View details for PubMedID 31915395

  View details for PubMedCentralID 5694650

• Stretchable and Flexible Buckypaper-Based Lactate Biofuel Cell for Wearable Electronics ADVANCED FUNCTIONAL MATERIALS Chen, X., Yin, L., Lv, J., Gross, A. J., Le, M., Gutierrez, N., Li, Y., Jeerapan, I., Giroud, F., Berezovska, A., O'Reilly, R. K., Xu, S., Cosnier, S., Wang, J. 2019; 29 (46)

  View details for DOI 10.1002/adfm.201905785

  View details for Web of Science ID 000496476200018

• Soft sensors form a network NATURE ELECTRONICS Lin, M., Gutierrez, N., Xu, S. 2019; 2 (8): 327-328

  View details for DOI 10.1038/s41928-019-0291-5

  View details for Web of Science ID 000481640000009

• A Biomimetic Soft Lens Controlled by Electrooculographic Signal ADVANCED FUNCTIONAL MATERIALS Li, J., Wang, Y., Liu, L., Xu, S., Liu, Y., Leng, J., Cai, S. 2019; 29 (36)

  View details for DOI 10.1002/adfm.201903762

  View details for Web of Science ID 000476009000001

• Wearable thermoelectrics for personalized thermoregulation. Science advances Hong, S., Gu, Y., Seo, J. K., Wang, J., Liu, P., Meng, Y. S., Xu, S., Chen, R. 2019; 5 (5): eaaw0536

  Abstract

  Thermoregulation has substantial implications for energy consumption and human comfort and health. However, cooling technology has remained largely unchanged for more than a century and still relies on cooling the entire space regardless of the number of occupants. Personalized thermoregulation by thermoelectric devices (TEDs) can markedly reduce the cooling volume and meet individual cooling needs but has yet to be realized because of the lack of flexible TEDs with sustainable high cooling performance. Here, we demonstrate a wearable TED that can deliver more than 10°C cooling effect with a high coefficient of performance (COP > 1.5). Our TED is the first to achieve long-term active cooling with high flexibility, due to a novel design of double elastomer layers and high-ZT rigid TE pillars. Thermoregulation based on these devices may enable a shift from centralized cooling toward personalized cooling with the benefits of substantially lower energy consumption and improved human comfort.

  View details for DOI 10.1126/sciadv.aaw0536

  View details for PubMedID 31114803

  View details for PubMedCentralID PMC6524982

• Biomembrane-Modified Field Effect Transistors for Sensitive and Quantitative Detection of Biological Toxins and Pathogens. ACS nano Gong, H., Chen, F., Huang, Z., Gu, Y., Zhang, Q., Chen, Y., Zhang, Y., Zhuang, J., Cho, Y. K., Fang, R. H., Gao, W., Xu, S., Zhang, L. 2019; 13 (3): 3714-3722

  Abstract

  The efforts of detecting bioactive targets with complex, dynamic, and unknown molecular profiles have inspired the development of various biosensor platforms. Herein, we report a cell-membrane-modified field effect transistor (FET) as a function-based nanosensor for the detection and quantitative measurement of numerous toxins and biological samples. By coating carbon nanotube FETs with natural red blood cell membranes, the resulting biomimetic nanosensor can selectively interact with and absorb broad-spectrum hemolytic toxins regardless of their molecular structures. Toxin-biomembrane interactions alter the local charge distribution at the FET surface in an ultrasensitive and concentration-dependent manner, resulting in a detection limit down to the femtomolar (fM) range. Accurate and quantitative measurements are enabled via a built-in calibration mechanism of the sensor, which overcomes batch-to-batch fabrication variations, and are demonstrated using three distinct toxins and various complex bacterial supernatants. The measured signals of bacterium-secreted proteins correlate linearly with the actual bacterial numbers, making the biosensor a nontraditional approach to rapidly detecting bacterial concentrations without a need to count bacterial colonies.

  View details for DOI 10.1021/acsnano.9b00911

  View details for PubMedID 30831025

• Materials and Structures toward Soft Electronics. Advanced materials (Deerfield Beach, Fla.) Wang, C., Wang, C., Huang, Z., Xu, S. 2018; 30 (50): e1801368

  Abstract

  Soft electronics are intensively studied as the integration of electronics with dynamic nonplanar surfaces has become necessary. Here, a discussion of the strategies in materials innovation and structural design to build soft electronic devices and systems is provided. For each strategy, the presentation focuses on the fundamental materials science and mechanics, and example device applications are highlighted where possible. Finally, perspectives on the key challenges and future directions of this field are presented.

  View details for DOI 10.1002/adma.201801368

  View details for PubMedID 30073715

• Highly Stable Battery Pack via Insulated, Reinforced, Buckling-Enabled Interconnect Array SMALL Yin, L., Seo, J., Kurniawan, J., Kumar, R., Lv, J., Xie, L., Liu, X., Xu, S., Meng, Y. S., Wang, J. 2018; 14 (43): e1800938

  Abstract

  This work describes a flexible and stretchable battery pack configuration that exhibits highly stable performance under large deformation up to 100% biaxial stretching. Using stress-enduring printable inks and serpentine interconnects, the new screen-printing route offers an attractive solution for converting rigid battery units into a flexible, stretchable energy storage device. Coin-cell lithium ion batteries are thus assembled onto the island regions of a screen-printed, buckling-enabled, polymer-reinforced interconnect "island-bridge" array. Most of the strain on the new energy-storage device is thus accommodated by the stress-enduring serpentine structures, and the array is further reinforced by mechanically strong "backbone" layers. Battery pack arrays are assembled and tested under different deformation levels, demonstrating a highly stable performance (<2.5% change) under all test conditions. A light emitting diode band powered by the battery pack is tested on-body, showing uninterrupted illumination regardless of any degrees of deformation. Moreover, battery-powered devices that are ultrastable under large deformation can be easily fabricated by incorporating different electronics parts such as sensors or integrated circuits on the same platform. Such ability to apply traditionally rigid, bulky lithium ion batteries onto flexible and stretchable printed surfaces holds considerable promise for diverse wearable applications.

  View details for DOI 10.1002/smll.201800938

  View details for Web of Science ID 000450110500015

  View details for PubMedID 29971916

• Monitoring of the central blood pressure waveform via a conformal ultrasonic device. Nature biomedical engineering Wang, C., Li, X., Hu, H., Zhang, L., Huang, Z., Lin, M., Zhang, Z., Yin, Z., Huang, B., Gong, H., Bhaskaran, S., Gu, Y., Makihata, M., Guo, Y., Lei, Y., Chen, Y., Wang, C., Li, Y., Zhang, T., Chen, Z., Pisano, A. P., Zhang, L., Zhou, Q., Xu, S. 2018; 2 (9): 687-695

  Abstract

  Continuous monitoring of the central-blood-pressure waveform from deeply embedded vessels, such as the carotid artery and jugular vein, has clinical value for the prediction of all-cause cardiovascular mortality. However, existing non-invasive approaches, including photoplethysmography and tonometry, only enable access to the superficial peripheral vasculature. Although current ultrasonic technologies allow non-invasive deep-tissue observation, unstable coupling with the tissue surface resulting from the bulkiness and rigidity of conventional ultrasound probes introduces usability constraints. Here, we describe the design and operation of an ultrasonic device that is conformal to the skin and capable of capturing blood-pressure waveforms at deeply embedded arterial and venous sites. The wearable device is ultrathin (240 μm) and stretchable (with strains up to 60%), and enables the non-invasive, continuous and accurate monitoring of cardiovascular events from multiple body locations, which should facilitate its use in a variety of clinical environments.

  View details for DOI 10.1038/s41551-018-0287-x

  View details for PubMedID 30906648

  View details for PubMedCentralID PMC6428206

• Three-dimensional integrated stretchable electronics NATURE ELECTRONICS Huang, Z., Hao, Y., Li, Y., Hu, H., Wang, C., Nomoto, A., Pan, T., Gu, Y., Chen, Y., Zhang, T., Li, W., Lei, Y., Kim, N., Wang, C., Zhang, L., Ward, J. W., Maralani, A., Li, X., Durstock, M. F., Pisano, A., Lin, Y., Xu, S. 2018; 1 (8): 473-480

  View details for DOI 10.1038/s41928-018-0116-y

  View details for Web of Science ID 000444080500014

• Controlled Homoepitaxial Growth of Hybrid Perovskites. Advanced materials (Deerfield Beach, Fla.) Lei, Y., Chen, Y., Gu, Y., Wang, C., Huang, Z., Qian, H., Nie, J., Hollett, G., Choi, W., Yu, Y., Kim, N., Wang, C., Zhang, T., Hu, H., Zhang, Y., Li, X., Li, Y., Shi, W., Liu, Z., Sailor, M. J., Dong, L., Lo, Y. H., Luo, J., Xu, S. 2018; 30 (20): e1705992

  Abstract

  Organic-inorganic hybrid perovskites have demonstrated tremendous potential for the next-generation electronic and optoelectronic devices due to their remarkable carrier dynamics. Current studies are focusing on polycrystals, since controlled growth of device compatible single crystals is extremely challenging. Here, the first chemical epitaxial growth of single crystal CH3 NH3 PbBr3 with controlled locations, morphologies, and orientations, using combined strategies of advanced microfabrication, homoepitaxy, and low temperature solution method is reported. The growth is found to follow a layer-by-layer model. A light emitting diode array, with each CH3 NH3 PbBr3 crystal as a single pixel, with enhanced quantum efficiencies than its polycrystalline counterparts is demonstrated.

  View details for DOI 10.1002/adma.201705992

  View details for PubMedID 29611280

• Stretchable ultrasonic transducer arrays for three-dimensional imaging on complex surfaces. Science advances Hu, H., Zhu, X., Wang, C., Zhang, L., Li, X., Lee, S., Huang, Z., Chen, R., Chen, Z., Wang, C., Gu, Y., Chen, Y., Lei, Y., Zhang, T., Kim, N., Guo, Y., Teng, Y., Zhou, W., Li, Y., Nomoto, A., Sternini, S., Zhou, Q., Pharr, M., di Scalea, F. L., Xu, S. 2018; 4 (3): eaar3979

  Abstract

  Ultrasonic imaging has been implemented as a powerful tool for noninvasive subsurface inspections of both structural and biological media. Current ultrasound probes are rigid and bulky and cannot readily image through nonplanar three-dimensional (3D) surfaces. However, imaging through these complicated surfaces is vital because stress concentrations at geometrical discontinuities render these surfaces highly prone to defects. This study reports a stretchable ultrasound probe that can conform to and detect nonplanar complex surfaces. The probe consists of a 10 × 10 array of piezoelectric transducers that exploit an "island-bridge" layout with multilayer electrodes, encapsulated by thin and compliant silicone elastomers. The stretchable probe shows excellent electromechanical coupling, minimal cross-talk, and more than 50% stretchability. Its performance is demonstrated by reconstructing defects in 3D space with high spatial resolution through flat, concave, and convex surfaces. The results hold great implications for applications of ultrasound that require imaging through complex surfaces.

  View details for DOI 10.1126/sciadv.aar3979

  View details for PubMedID 29740603

  View details for PubMedCentralID PMC5938227

• Materials science. Assembly of micro/nanomaterials into complex, three-dimensional architectures by compressive buckling. Science (New York, N.Y.) Xu, S., Yan, Z., Jang, K. I., Huang, W., Fu, H., Kim, J., Wei, Z., Flavin, M., McCracken, J., Wang, R., Badea, A., Liu, Y., Xiao, D., Zhou, G., Lee, J., Chung, H. U., Cheng, H., Ren, W., Banks, A., Li, X., Paik, U., Nuzzo, R. G., Huang, Y., Zhang, Y., Rogers, J. A. 2015; 347 (6218): 154-9

  Abstract

  Complex three-dimensional (3D) structures in biology (e.g., cytoskeletal webs, neural circuits, and vasculature networks) form naturally to provide essential functions in even the most basic forms of life. Compelling opportunities exist for analogous 3D architectures in human-made devices, but design options are constrained by existing capabilities in materials growth and assembly. We report routes to previously inaccessible classes of 3D constructs in advanced materials, including device-grade silicon. The schemes involve geometric transformation of 2D micro/nanostructures into extended 3D layouts by compressive buckling. Demonstrations include experimental and theoretical studies of more than 40 representative geometries, from single and multiple helices, toroids, and conical spirals to structures that resemble spherical baskets, cuboid cages, starbursts, flowers, scaffolds, fences, and frameworks, each with single- and/or multiple-level configurations.

  View details for DOI 10.1126/science.1260960

  View details for PubMedID 25574018

• Soft microfluidic assemblies of sensors, circuits, and radios for the skin. Science (New York, N.Y.) Xu, S., Zhang, Y., Jia, L., Mathewson, K. E., Jang, K. I., Kim, J., Fu, H., Huang, X., Chava, P., Wang, R., Bhole, S., Wang, L., Na, Y. J., Guan, Y., Flavin, M., Han, Z., Huang, Y., Rogers, J. A. 2014; 344 (6179): 70-4

  Abstract

  When mounted on the skin, modern sensors, circuits, radios, and power supply systems have the potential to provide clinical-quality health monitoring capabilities for continuous use, beyond the confines of traditional hospital or laboratory facilities. The most well-developed component technologies are, however, broadly available only in hard, planar formats. As a result, existing options in system design are unable to effectively accommodate integration with the soft, textured, curvilinear, and time-dynamic surfaces of the skin. Here, we describe experimental and theoretical approaches for using ideas in soft microfluidics, structured adhesive surfaces, and controlled mechanical buckling to achieve ultralow modulus, highly stretchable systems that incorporate assemblies of high-modulus, rigid, state-of-the-art functional elements. The outcome is a thin, conformable device technology that can softly laminate onto the surface of the skin to enable advanced, multifunctional operation for physiological monitoring in a wireless mode.

  View details for DOI 10.1126/science.1250169

  View details for PubMedID 24700852

• Stretchable batteries with self-similar serpentine interconnects and integrated wireless recharging systems NATURE COMMUNICATIONS Xu, S., Zhang, Y., Cho, J., Lee, J., Huang, X., Jia, L., Fan, J. A., Su, Y., Su, J., Zhang, H., Cheng, H., Lu, B., Yu, C., Chuang, C., Kim, T., Song, T., Shigeta, K., Kang, S., Dagdeviren, C., Petrov, I., Braun, P. V., Huang, Y., Paik, U., Rogers, J. A. 2013; 4

  Abstract

  An important trend in electronics involves the development of materials, mechanical designs and manufacturing strategies that enable the use of unconventional substrates, such as polymer films, metal foils, paper sheets or rubber slabs. The last possibility is particularly challenging because the systems must accommodate not only bending but also stretching. Although several approaches are available for the electronics, a persistent difficulty is in power supplies that have similar mechanical properties, to allow their co-integration with the electronics. Here we introduce a set of materials and design concepts for a rechargeable lithium ion battery technology that exploits thin, low modulus silicone elastomers as substrates, with a segmented design in the active materials, and unusual 'self-similar' interconnect structures between them. The result enables reversible levels of stretchability up to 300%, while maintaining capacity densities of ~1.1 mAh cm(-2). Stretchable wireless power transmission systems provide the means to charge these types of batteries, without direct physical contact.

  View details for DOI 10.1038/ncomms2553

  View details for Web of Science ID 000316616400111

  View details for PubMedID 23443571

• One-dimensional ZnO nanostructures: Solution growth and functional properties NANO RESEARCH Xu, S., Wang, Z. 2011; 4 (11): 1013-1098

  View details for DOI 10.1007/s12274-011-0160-7

  View details for Web of Science ID 000296646000001

• Oxide nanowire arrays for light-emitting diodes and piezoelectric energy harvesters PURE AND APPLIED CHEMISTRY Xu, S., Wang, Z. 2011; 83 (12): 2171-2198

  View details for DOI 10.1351/PAC-CON-11-08-17

  View details for Web of Science ID 000298742600005

• Piezoelectric-nanowire-enabled power source for driving wireless microelectronics. Nature communications Xu, S., Hansen, B. J., Wang, Z. L. 2010; 1: 93

  Abstract

  Harvesting energy from irregular/random mechanical actions in variable and uncontrollable environments is an effective approach for powering wireless mobile electronics to meet a wide range of applications in our daily life. Piezoelectric nanowires are robust and can be stimulated by tiny physical motions/disturbances over a range of frequencies. Here, we demonstrate the first chemical epitaxial growth of PbZr(x)Ti(1-x)O(3) (PZT) nanowire arrays at 230 °C and their application as high-output energy converters. The nanogenerators fabricated using a single array of PZT nanowires produce a peak output voltage of ~0.7 V, current density of 4 μA cm(-2) and an average power density of 2.8 mW cm(-3). The alternating current output of the nanogenerator is rectified, and the harvested energy is stored and later used to light up a commercial laser diode. This work demonstrates the feasibility of using nanogenerators for powering mobile and even personal microelectronics.

  View details for DOI 10.1038/ncomms1098

  View details for PubMedID 20981021

• Self-powered nanowire devices. Nature nanotechnology Xu, S., Qin, Y., Xu, C., Wei, Y., Yang, R., Wang, Z. L. 2010; 5 (5): 366-73

  Abstract

  The harvesting of mechanical energy from ambient sources could power electrical devices without the need for batteries. However, although the efficiency and durability of harvesting materials such as piezoelectric nanowires have steadily improved, the voltage and power produced by a single nanowire are insufficient for real devices. The integration of large numbers of nanowire energy harvesters into a single power source is therefore necessary, requiring alignment of the nanowires as well as synchronization of their charging and discharging processes. Here, we demonstrate the vertical and lateral integration of ZnO nanowires into arrays that are capable of producing sufficient power to operate real devices. A lateral integration of 700 rows of ZnO nanowires produces a peak voltage of 1.26 V at a low strain of 0.19%, which is potentially sufficient to recharge an AA battery. In a separate device, a vertical integration of three layers of ZnO nanowire arrays produces a peak power density of 2.7 mW cm(-3). We use the vertically integrated nanogenerator to power a nanowire pH sensor and a nanowire UV sensor, thus demonstrating a self-powered system composed entirely of nanowires.

  View details for DOI 10.1038/nnano.2010.46

  View details for PubMedID 20348913